1. Field of the Invention
The present invention relates to a method for modeling a tire model used for computer simulation of a pneumatic tire and a simulation method, and more particularly, to a method for more precisely analyzing a tread portion of a pneumatic tire.
2. Description of the Related Art
In recent years, various computer simulations of pneumatic tires have been proposed. The simulation is carried out using a numerical analyzing tire model (mesh model) obtained by dividing a tire into a finite number of small elements. FIG. 19 is a sectional view taken along a tire equatorial plane of a visualized tire model 20. The tire model 20 comprises a toroidal main body model 22 divided into N (N is integer not less than 2) in a circumferential direction of the tire, and a pattern model 24 divided into M (M>N) in the circumferential direction. The main body model 22 is made by dividing a toroidal main body of a pneumatic tire equally in a circumferential direction of the tire using a finite number of elements. Further, the pattern model 24 is made by dividing a circumferentially extending tread pattern of the pneumatic tire equally in a circumferential direction of the tire using a finite number of elements.
Since the tread pattern has much effect on the running performance, the tread pattern model 24 is divided into more elements than the main body model 22 to precisely analyze the performance in the simulation. Further, since the number of elements of the main body model 22 is smaller than that of the pattern model 24, there is a merit that calculation time required for the simulation can be shortened.
According to the tire model 20 shown in FIG. 19, however, a thickness of the pattern model 24 measured in the normal direction from a radially outer surface of the body model 22 is not constant based on a difference (M/N=4 in this example) of the division numbers between the main body models 22 and the pattern models 24. That is, the pattern model 24 has a thickness T1 at the nodal point of the body model 22, but has a thickness T2 (T2>T1) at the intermediate position in the circumferential direction of the body model 22. In such a tire model 20, a high ground-contact pressure may be calculated at the portion of the greater thickness T2 of the pattern model 24, but a lower ground-contact pressure may be calculated at the portion of the small thickness T1. Such a calculation result alienates from the actual ground-contact pressure distribution and deteriorates the simulation precision.
In order to solve this problem, it is conceived that the number of divisions N of the main body model 22 in the tire circumferential direction and the number of divisions M of the pattern model 24 are set equal to each other. However, this method increases the number of elements of the tire model 20, and increases the calculation time required for the simulation and a memory consumption amount. If the number of divisions M of the pattern model 24 in the tire circumferential direction and the number N of divisions of the body model 22 are set equal to each other, deformation of the pattern model 24 can not be simulated precisely and in detail.